DE 19833983 A1 generally discloses a rotary control as a power control or operating device for an electrical appliance, for example for a hob or cook-top.
DE 29605163 U1, discloses a rotary control having an optical waveguide that is used for indicating the transfer of the rotary position of an operating unit. The optical waveguide channels light in the vicinity of the rotational axis of the rotary control. The light is fed from below into the optical waveguide in the downwards direction as a function of the rotary position. Beneath an outer surface in the vicinity of the rotation axis of the rotary control, a light source is provided along with photosensitive sensors for detecting position of the rotary control. The sensors record the light passing through the optical waveguide and emitted at the underside of the operating unit as a function of the rotary position of the rotary control at different locations . DE 10212954 A1 describes the use of an operating unit with microprocessor, which detects the rotary position of a rotary toggle of the operating unit relative to an angle-stable bearing device or outer surface on which the rotary toggle is mounted, and relays it to a receiver located below the outer surface. These operating devices are particularly suitable for use with electrical heating appliances with an outer surface (such as a cook-top), because these devices make it possible to for a user to operate the electrical heating appliances by means of operating units located on the glass ceramic plate and without it being necessary to provide openings in the glass plate.
Known operating devices are considered disadvantageous in that they only permit the recording or detecting of one angular position or one position change. Thus, it is difficult to implement more complex functions than the power control of, for example, a hob or cook-top.
The problem of the invention is to provide an aforementioned operating device and a method able to avoid the prior art problems and, in particular, an operating device for an electrical appliance, which is superior to the prior art with respect to operability or operating method.